<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
/* 默认状态 */
a:link{
    color:red;
}

/* 访问后状态 */
a:visited{
    color:grey;
}

/* 鼠标移入 */
a:hover{
    color:yellow;
}

/* 鼠标按下但不松手 */
a:active{
    color:blue;
}
</style>
<body>
    <a href="#">一个连接</a>
</body>
</html>